MXPA99011012A - Article coated with multilayer coating - Google Patents

Abstract

An article having a coating comprising at least one nickel layer, a chrome layer, a layer comprised of titanium or titanium alloy, a layer comprised of titanium compound or titanium alloy compound, and a zirconium compound or zirconium alloy compound layer.

Description

COATED ARTICLE WITH MULTI-LAYER COATINGS Field of the Invention This invention relates to decorative and protective coatings.

Background of the Invention It is currently the practice with various brass items such as lamps, trivets, spigots, door knobs, door handles, door lock shields and the like, burnishing and polishing the surface of the item first to a high luster and then applying a coating protective organic, such - as one comprised of acrylics, urethanes, epoxies and the like, on this polished surface. This system has the drawback that the required operation of burnishing and polishing, particularly if the article is of a complex shape, is very laborious.

Also, the known organic coatings are not as durable as desired nor wear resistant REF: 32093 These deficiencies are remedied by a coating containing a nickel base coat and a non-precious refractory metal compound, such as zirconium nitride. titanium nitride and zirconium-titanium alloy nitride top coat However, it has been found that when titanium is present in the coating, such as titanium nitride or as zirconium-titanium alloy nitride, in corrosive environments the The coating can undergo galvanic corrosion.This galvanic corrosion makes the coating virtually useless.It has surprisingly been found that the presence of a layer comprised of the zirconium compound, such as zirconium nitride, or a zirconium alloy compound on the layers containing the Composite titanium or titanium alloy compound, reduces signifi cativamente or eliminates galvanic corrosion.

Brief Description of the Invention The present invention is directed to a decorative protective coating for a substrate, particularly a metallic substrate.

More particularly, it is directed to a substrate, particularly a metallic substrate such as brass, which has on at least a portion of its surface a coating comprised of multiple, superimposed metal layers of certain specific types of metals or metal compounds, wherein at least one of the layers contains titanium or a titanium alloy. The coating is decorative and also provides resistance against corrosion, wear and against chemicals. In one embodiment the coating gives the appearance of polished brass with a golden hue, for example it has a golden-brass color tone. In this way, a surface of the article having the coating on it simulates polished brass with a golden hue. A first layer deposited directly on the surface of the substrate is comprised of nickel. The first layer may be monolithic, for example, a single nickel layer, or it may consist of two different layers of nickel, such as a layer of semi-gloss nickel deposited directly on the surface of the substrate and a layer of bright nickel superimposed on the surface of the substrate. semi-gloss nickel layer. On the nickel layer is a layer comprised of chromium. On the chromium layer is a fixing or adhesion layer comprised of titanium or titanium alloy. On the titanium or titanium alloy layer is a layer comprised of titanium compound or titanium alloy compound. On the layer of the titanium compound or the titanium alloy compound is a thin layer comprised of zirconium compound or zirconium alloy compound. This layer works to reduce or eliminate galvanic corrosion.

BRIEF DESCRIPTION OF THE INVENTION Figure 1 is a cross-sectional view, not to scale, of the multilayer coating on a substrate.

Brief Description of the Drawing Figure 1 is a cross-sectional view, not to scale, of the multilayer coating on a substrate.

Description of the Preferred Modality The substrate 12 can be any of plastic, metal or metallic alloy. Illustrative of the metal and metal alloy substrates are copper, steel, brass, tungsten, nickel alloys and the like. In one embodiment, the substrate is brass. A layer of nickel 13 deposited on the surface of the substrate 12 by conventional and well-known electroplating processes. These processes include the use of a conventional electroplating bath such as, for example, a Watts bath as the plating solution. Typically, such baths contain nickel sulfate, nickel chloride, and boric acid dissolved in water. All chloride, sulphamate and fluoroborate plating solutions can also be used. These baths may optionally include a number of well-known and conventionally used compounds such as leveling agents, brighteners and the like. To produce the specularly bright nickel layer, at least one class I polish and at least one class II polish is added to the plating solution. Class 1 polishes are organic compounds containing sulfur. Class II polishes are organic compounds that do not contain sulfur. Class II polishes can also cause leveling, and when added to the plating bath without the sulfur-containing class I polishes, result in semi-glossy nickel deposits. These class I brighteners include alkyl-naphthalene- and benzenesulfonic acid. Benzene- and naphthalene-di- and trisulonic acids, benzene and naphthalene sulfonamides, and sulfonamides such as saccharin, vinyl- and allyl-sulfonamides and sulfonic acids. Class II polishes are generally unsaturated organic materials such as, for example, acetylenic and ethylenic alcohols, ethoxylated or propoxylated acetylenic alcohols, coumarins and aldehydes. These class I and class II brighteners are well known to those of skill in the art and are readily available commercially. These are described, inter alia, in U.S. Patent No. 4,421,611 incorporated by reference herein.

The nickel layer 13 may be comprised of a single layer of nickel such as, for example, bright nickel, or it may be comprised of two different nickel layers such as a semi-gloss nickel layer and a bright nickel layer. In the figures the layer 14 is comprised of semi-glossy nickel while the layer 16 is comprised of bright nickel. This double nickel deposit provides enhanced protection against corrosion to the underlying substrate. The sheet 14, sulfur-free, semi-glossy, is deposited by conventional electroplating processes directly on the surface of the substrate 12. The substrate 12 containing the layer 14 of semi-gloss nickel is then plated in a bright nickel plating bath, and the The bright nickel layer 16 is deposited on the semi-gloss nickel layer 14, also by conventional electroplating processes. The thickness of the nickel layer 13 is generally in the range of about 2.54 micrometers (μ) ((0.0001 inch) 100 millionths of an inch), preferably from about 3.81 μm (0.00015 inches) to about 88.9 μm (0.0035 inches).

In the embodiment where the double nickel layer is used, the thickness of the semi-glossy nickel layer and the bright nickel layer is an effective thickness to provide improved protection against corrosion. In general, the thickness of the semi-gloss nickel layer 14 is at least about 1.25 μm (0.00005 inches), preferably at least about 2.54 μm (0.0001 inches), and more preferably at least about 3.81 μm (0.00015 inches). The upper thickness limit is not critical and is governed by secondary considerations, such as cost and appearance. In general, however, a thickness of about 38.1 μm (0.0015 inches), preferably about 25.4 μm (0.001 inches), and more preferably about 19.05 μm (0.0075 inches) should not be exceeded. The bright nickel layer. The bright nickel layer 16 generally has a thickness of at least about 1.25 μm (0.00005 inches), preferably at least about 3.17 μm (0.000125 inches), and more preferably at least about 6.35 μm. (0.00025 inches). The upper thickness range of the bright nickel layer is not critical and is generally controlled by considerations such as cost. In general, however, thicknesses of about 63.5 μm (0.0025 inches), preferably about 50.8 μm (0.002 inches), and more preferably about 38.1 μm (0.0015 inches) should not be issued. The bright nickel layer 16 also functions as a leveling layer which tends to cover or fill imperfections in the substrate. Placed on the nickel layer 13, particularly the bright nickel layer, is a layer 22 comprised of chromium. The chromium layer 22 can be deposited on the layer 13 by conventional and well-known chromium electroplating techniques. These techniques, together with various chromium plating baths are described in Brassard, "Decorative Electroplating - A Process in Transition", Metal Finishing, pp. 105-108, June 1998; Zaki, "Chromium Plating", PF Directory, pp. 146-160; and in U.S. Patent Nos. 4,460,438, 4,234,396 and 4,093,522, all of which are incorporated by reference herein. Chromium plated baths are well known and commercially available. A typical chromium plating bath contains chromic acid or salts thereof, and a catalyst ion such as sulfate or fluoride. The catalyst ions can be provided by sulfuric acid or its salts and fluosilic acid. The baths can be operated at a temperature of approximately 44 ° C (112 ° F) to 47 (116 ° F). Typically in chrome plating a current of approximately 1614 amps / m2 (150 amps per square meter) is used approximately 5 to 9 volts are used. The chromium layer 22 serves to provide structural integrity to the vapor deposited layers or reduce or eliminate the plastic deformation of the coating. The nickel layer 13 is relatively smooth in comparison to the layer 30 of the titanium compound or the titanium alloy compound. In this way, an object that collides, that crashes or presses on the layer 30 will not penetrate this relatively hard layer, but this force will be transferred to the underlying relatively soft nickel layer 13, causing the plastic deformation of this layer. The chromium layer 22, which is relatively harder than the nickel layer, will in general resist the plastic deformation of the nickel layer 13.

The chromium layer 22 has a thickness at least effective to provide structural integrity and reduce plastic deformation of the coating. This thickness is at least about 0.05 μm (0.000002 inches), preferably and at least about 0.127 μm (0.000005 inches), and more preferably at least about 0.203 μm (0.000008 inches). In general, the upper range of thickness is not critical and is determined by secondary considerations such as cost. However, the thickness of the chromium layer should not generally exceed about 1,524 μm (0.00006 inches), preferably about 1.27 μm. (0.00005 inches), and more preferably 1016 μm (0.00004 inches). Placed on the chrome layer 22 is a fixing layer 28 comprised of titanium or titanium alloy. The fixing layer 28 functions, inter alia, to improve the adhesion of the layer 30, comprised of the titanium compound or the titanium alloy compound, to the chromium layer 22. In general, this thickness is at least about 6.35. x 10 ~ 3 micrometers (0.25 millionths of an inch) preferably at least about 1.27 x 10 - 2 micrometers (0.5 millionths of an inch) and more preferably at least about 2.54 x 10-2 micrometers (0.0000001 of an inch). The upper thickness range is not critical, and is generally dependent on considerations such as cost and appearance. In general, however, layer 28 should not be thicker than approximately 1.27 micrometers (50 millionths of an inch), preferably about 0.38 micrometers (15 millionths of an inch), and more preferably 0.25 micrometers (10 millionths of an inch). On the fixing layer 28 is the layer 30 comprised of titanium compound or titanium alloy compound. The layer 30 provides resistance to wear and abrasion, and the desired color or appearance, such as, for example, a color tinged with a golden hue. The layer 30 has an effective thickness to provide resistance to abrasion and wear, and to provide the required color. The color depends on the composition of the layer 30. In this way, the titanium-zirconium nitride will provide a brass-colored color with a golden hue.

In general, layer 30 has a thickness of approximately 5.08 x 10 ~ 2 microns (2 millionths of an inch), preferably at least about 1.01 x 10"1 microns (4 millionths of an inch), and more preferably at least 1.52 x 10" 1 micrometer (6 millionths of an inch). The upper thickness range is not generally critical and is dependent on considerations such as cost. In general, a thickness of about 2.54 micrometers (100 millionths of an inch), preferably about 1.27 micrometers (50 millionths of an inch, and more preferably about 0.76 micrometers (30 millionths of an inch), should not be exceeded. titanium to form the titanium alloy or the titanium alloy compound are non-precious refractory metals.These include zirconium, hafnium, tantalum and tungsten.The titanium alloys generally comprise from about 10 to about 90 weight percent titanium and from about 90 to about 10 weight percent of another non-precious refractory metal, preferably from about 20 to about 80 weight percent of titanium and from about 80 to about 20 weight percent of another refractory metal. and the titanium alloy compounds include the oxides, nitr Uros, carbides and carbonitrides. In one embodiment the layers 30 are comprised of titanium-zirconium alloy nitrides and the layers 28 are comprised of titanium-zirconium alloy. In this embodiment, the titanium-zirconium alloy nitride layer has a brass color with a golden hue. One method for the formation of layers 28 and 30 is by the use of well-known and conventional vapor deposition techniques, such as physical vapor deposition and chemical vapor deposition. Physical vapor deposition processes include cathodic deposition and cathodic arc deposition. In a process of the present invention, cathodic deposition or cathodic deposition evaporation is used to deposit a layer 28 of titanium or titanium alloy, followed by reactive cathodic deposition or reactive cathodic arc evaporation to deposit a layer 30 of titanium alloy compound such as titanium-zirconium nitride or titanium compound such as titanium nitride. To form the layer 30 in which the titanium compound or the titanium alloy compound are the nitrides, the nitrogen gas is introduced by the deposition of the vapor such as reactive cathodic deposition or reactive evaporation by cathodic arc at a value or flow rate desired to form titanium nitride or titanium alloy nitride. Above the layer 30 is the layer 34. The layer 34 is comprised of a zirconium compound or a zirconium alloy compound. The zirconium compounds or the zirconium alloy compounds are the oxides, nitrides, carbides and carbonitrides. The metals that are alloyed with zirconium to form the zirconium alloy compounds are refractory precious metal compounds, excluding titanium. The zirconium alloy comprises from about 30 to about 90 weight percent zirconium, the rest being non-precious refractory metal other than titanium; preferably from about 40 to about 90 weight percent zirconium, the rest being non-precious refractory metal other than titanium; and more preferably from about 50 to about 90 weight percent zirconium, the rest being non-precious refractory metal other than titanium. The layer 34 may be, for example, zirconium nitride when the layer 30 is zirconium-titanium alloy nitride. The layer 34 is very thin. This is thin enough so that it is non-opaque, translucent or transparent in order to allow the color of the layer 30 to be observed. However, it must be thick enough to significantly reduce or eliminate the galvanic corrosion. In general, layer 34 has a thickness of about 1.77 X 10"3 μm (0.07 millionths of an inch) to about 1.77.

X 10 - 2 μm (0.7 millionths of an inch) preferably from about 5.08 X 10 μm (0.2 millionths of an inch) to about 7.62 X 10 ~ 3 μm (0.3 millionths of an inch). The layer 34 can be deposited by well-known and conventional vapor deposition techniques, including physical vapor deposition and chemical vapor deposition such as, for example, reactive cathodic deposition and cathodic arc reactive evaporation. The techniques of cathodic deposition and the equipment for these are described, among others in J. Vossen and W. Kern "Thin Film Processes II" Academic Press, 1991; R. Boxman et al., "Handbook of Vacuum Are Science and Technology", Noyes Pub., 1995; and U.S. Patent Nos. 4,162,954 and 4,591,418, all of which are incorporated by reference herein. In summary, in the process of cathodic deposition a target of refractory metal (such as titanium or zirconium), which is the cathode, and the substrate are placed in a vacuum chamber. The air in the chamber is evacuated to produce vacuum conditions in the chamber. An inert gas, such as Argon, is introduced into the chamber. The particles of the gas are ionized and accelerated towards the target to dislodge the titanium or zirconium atoms. The evicted target material is then typically deposited as a coating film on the substrate. In cathodic arc evaporation, an electric arc typically of several hundred amperes is struck on the metal cathode surface such as zirconium or titanium. The arc vaporizes the cathodic material, which is then condensed on the substrates forming a coating. Reactive cathodic arc evaporation and reactive cathodic deposition are generally similar to ordinary sputtering and cathodic arc evaporation, except that a reactive gas is introduced into the chamber, which reacts with the target material dislodged. Thus, in the case where the zirconium nitride is layer 32, the cathode is comprised of zirconium, and nitrogen is the reactive gas introduced into the chamber. By controlling the amount of nitrogen available to react with the zirconium, the color of the zirconium nitride can be adjusted to be similar to that of the brass of various shades. In order that the invention can be more easily understood, the following example is provided. The example is illustrative and does not limit the invention to it.

EXAMPLE 1 Brass spouts are placed in a conventional soaking bath, containing standard and well known soaps, detergents, flocculants and the like, which is maintained at a pH of 8.9-9.2 and at a temperature of about 63 to 93 ° C. (145 to 200 ° F) for 10 minutes. The brass spouts are then placed in an alkaline, ultrasonic, conventional cleaning bath. The ultrasonic cleaning bath has a pH of 8.9 to 9.2, is maintained at a temperature of about 71 to 82 ° C (160 to 180 ° F), and contains conventional, well-known soaps, detergents, deflocculators and the like. After the ultrasonic cleaning, the spouts are rinsed and placed in a conventional, alkaline, electro-cleaning bath for approximately 50 seconds. The electro-cleaning bath is maintained at a temperature of about 60 to 82 ° C (140 to 180 ° F), at a pH of about 10.5 to 11.5, and contains standard and conventional detergents. The spouts are then rinsed and placed in a conventional acid activator bath for approximately 20 seconds. The acid activator bath has a pH of about 2.0-3.0, and is at room temperature, and contains an acid salt based on sodium fluoride. The spouts are then placed in a plating bath with bright nickel, conventional and standard, for approximately 12 minutes. The bright nickel bath is generally a conventional bath which is maintained at a temperature of about 55 to 66 ° C (130 to 150 ° F), a pH of about 4.0 to 4.8, contains NiS04, NiCl2, boric acid, and brighteners. A layer of bright nickel of an average thickness of approximately 10.16 μm (400 millionths of an inch) is deposited on the spigots. The bright nickel plated spouts are rinsed three times and then placed in a commercially available, conventional hexavalent chromium plating bath using conventional chrome plating equipment for approximately 7 minutes. The hexavalent chromium bath is a conventional and well known bath containing approximately 242.6 g / liter (32 oz / gal) of chromic acid. The bath also contains the conventional and well known chrome plating additives. The bath is maintained at a temperature of about 44 to 47 ° C (112 to 116 ° F), and utilizes a mixed sulfate / fluoride catalyst. The ratio of chromic acid to sulfate is approximately 200: 1. A chromium layer of approximately 0.254 μm (10 millionths of an inch) is deposited on the substrate of the bright nickel layer. The spouts are perfectly rinsed in deionized water and then dried. The chromium plated spouts are placed in a plating vessel by cathodic arc evaporation. The container is generally a cylindrical housing containing a vacuum chamber, which is adapted to be evacuated by means of pumps. An argon gas source is connected to the chamber by an adjustable valve to vary the gas flow rate. A cylindrical, zirconium-titanium alloy cathode is mounted in the center of the chamber and connected to the negative outputs of a variable direct current (D.C.) power supply. The positive side of the power supply is connected to the wall of the chamber. The cathode material comprises zirconium and titanium.

The plated spouts are mounted on spindles, 16 of which are mounted on a ring around the outer side of the cathode. The entire ring rotates around the cathode, while each spindle also rotates around its own axis, resulting in a so-called planetary motion that provides uniform exposure to the cathode for the multiple spigots mounted around each spindle. The ring rotates typically at several revolutions per minute, while each spindle performs several revolutions per revolution of the ring. The spouts are electrically isolated from the chamber and provided with rotating contacts, so that a bias voltage can be applied to the substrates during the coating. The vacuum chamber is evacuated to a pressure of approximately 5 x 10"3 millibars and heated to approximately 150 ° C. The electroplated spouts are then subjected to a high polarization plasma arc cleaning in which a bias voltage is applied. (Negative) of approximately 500 volts to the electroplated spigots, while an arc of approximately 500 amperes is struck and held on the cathode.The duration of cleaning is approximately five minutes.Argon gas is introduced at a rate sufficient to maintain a pressure of approximately 3 x 10 ~ 2 millibars A zirconium-titanium alloy layer having an average thickness of approximately 0.1 μm (4 millionths of an inch) is deposited on the chromium-plated spigots for a period of three minutes. The process of cathodic arc deposition involves the application of DC energy to the cathode to achieve a current flow of approximately 500 amperes, introducing the argon gas into the container to maintain the pressure in the vessel at about lxlO-2 millibars, and rotating the spouts in a planetary manner, described above. After the zirconium titanium alloy layer is deposited, a thicker "colored layer" of zirconium-titanium nitride compound is deposited thereon. A nitrogen flow is introduced into the vacuum chamber while the arc discharge continues at approximately 500 amps. The flow rate of the nitrogen is adjusted high enough to fully react the atoms of the zirconium and titanium alloy, reaching the substrate to form the zirconium-titanium nitride compound. The total time for the deposition is approximately 30 minutes. The arch is extinguished at the end of this deposition period, the vacuum chamber is ventilated and the coated substrates are removed. After the zirconium-titanium nitride compound layer is deposited, a non-optically dense, thin, final, zirconium nitride instantaneous layer is deposited to provide increased corrosion resistance, and to achieve the desired final color. The coated substrate parts are placed inside another chamber equipped with a cylindrical cathode lens composed mainly of zirconium metal. The chamber is evacuated at the pressures previously described, as well as the cleaned parts again when clamping them to high polarization arc plasma as described at the beginning. After the cleaning process is completed, the cathodic arc deposition process is repeated with flows of nitrogen gas and argon set high enough to provide complete or almost complete reaction of the zirconium metal to the zirconium nitride compound. This instantaneous process is carried out for a period of one to three minutes. Finally, the arch is extinguished, and the chamber is ventilated and the coated substrates are removed. While certain embodiments of the invention have been described for purposes of illustration, it should be understood that various embodiments and modifications may exist within the general scope of the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Claims (14)

RE IVINDICATIONS Having described the invention as above, the content of the following claims is claimed as property:

1. An article, characterized in that it has on at least a portion of its surface a coating comprising: at least one layer comprised of nickel; a layer comprised of chromium; a layer comprised of titanium or titanium alloy; a layer comprised of titanium compound or titanium alloy compound; and a layer comprised of zirconium compound or zirconium alloy compound.

2. The article according to claim 1, characterized in that the titanium compound is titanium nitride and the titanium alloy compound is titanium-zirconium alloy nitride.

3. The article according to claim 2, characterized in that the titanium alloy is titanium-zirconium alloy.

4. The article according to claim 3, characterized in that the zirconium compound is zirconium nitride.

5. The article according to claim 3, characterized in that the zirconium alloy compound is zirconium alloy nitride.

6. The article according to claim 1, characterized in that at least one layer comprised of nickel is comprised of bright nickel.

7. An article having on at least a portion of its surface a coating, characterized in that it comprises: a layer comprised of semi-glossy nickel; a layer comprised of bright nickel; a layer comprised of chromium; a layer comprised of titanium or titanium alloy; a layer comprised of titanium compound or titanium alloy compound; and a layer comprised of zirconium compound or zirconium alloy compound.

8. The article according to claim 7, characterized in that the titanium compound is titanium nitride.

9. The article according to claim 8, characterized in that the titanium alloy compound is composed of titanium-zirconium alloy.

10. The article according to claim 9, characterized in that the titanium-zirconium alloy compound is titanium-zirconium alloy nitride.

11. The article according to claim 10, characterized in that the zirconium compound is zirconium nitride.

12. The article according to claim 10, characterized in that the zirconium alloy compound is zirconium alloy nitride.

13. The article according to claim 7, characterized in that the zirconium compound is zirconium nitride.

14. The article according to claim 7, characterized in that the zirconium alloy compound is zirconium alloy nitride.